A new infectious disease problem emerged in October 2001. Bacillus anthracis spores used to intentionally sicken and, in five instances, kill individuals generally failed to infect the bioterrorists’ targets, highly visible members of the media and government. Rather, they infected people who handled contaminated mail, the vehicle used to transmit this agent. The emergence of a number of bacteria resistant to multiple antimicrobial agents has caused serious concern in the medical community. Nosocomial infections due to multidrug-resistant organisms have become a problem of increasing seriousness. In the early 1990s, Staphylococcus aureus strains resistant to all antimicrobial agents with the exception of vancomycin became a common cause of nosocomial infection. These organisms, called methicillin-resistant S. aureus (MRSA), along with another important nosocomial pathogen, Clostridium difficile, were treated with vancomycin. The resulting antimicrobial pressure is believed to have made a major contribution to the emergence of another nosocomial pathogen, vancomycin-resistant enterococci (VRE). Bacteremia due to this organism has a high mortality rate. Multidrug-resistant organisms, such as aminoglycoside-resistant Pseudomonas aeruginosa, have long been recognized as important nosocomial pathogen. The recognition of a variant of Creutzfeldt-Jakob disease in the United Kingdom and France, which has been associated with the consumption of beef from herds with bovine spongiform encephalopathy (BSE), has caused a reexamination of feeding practices of domestic animals. New variants of the influenza A virus may have emerged through recombination events between avian and human viral strains.

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